1. Field of the Invention
The present invention relates to an optical apparatus, and more particularly to an optical apparatus using a vertical light receiving element for coupling a light signal from a light source and then transforming the received light signal into an electric signal.
2. Description of the Related Art
In order to manufacture a light module of ultra-low cost, the light module must be manufactured in complete automatization, that is, in a chip mounting method. Two-dimensional optical coupling is necessary in optical coupling, such as optical coupling between a laser diode and a photodiode, between a fiber and a photodiode, and between a Planar Lightwave Circuit (PLC) and a photodiode, and so forth.
The optical coupling is needed to enable light signals emitted from light sources, such as a laser diode, fiber, a Planar Lightwave Circuit (PLC) device and the like, to arrive at a light receipt surface without experiencing any loss in the monitoring paths of the light signals, so as to be converted into optimal electric signals.
A Planar Lightwave Circuit (PLC) platform, which is essentially a Printed Circuit Board (PCB) with photo circuits, has been proposed to be used in a photo module for actualizing photoelectric transformation at a higher speed up to several gigabits per second.
FIG. 1 is a view showing a basic structure of a photo PCB forming a PLC platform according to the prior art. As shown, a PLC section 10 comprises a part of a substrate 8—that is, a right part of the substrate 8—and a quartz-based optical waveguide formed on the right part of the substrate 8 in which the quartz-based optical waveguide comprises upper clad layer 1, core layer 2 and lower clad layer 3. The PLC section 10 performs splitting/coupling functions for light signals.
A photo device mounting section 20 is positioned at another part of the substrate 8, that is, at a central part of the substrate 8. A photo device 4, such as a laser, a photodiode and so forth, is mounted on the photo device mounting section 20, and performs signal-transform functions from light signals to electric signals and vice versa. An electric distributing section, which is the rest part of the substrate 8, connects the photo device 4 with a driving circuit and transmits high frequency signals over GHz.
Further, a silicon terrace 7 having a section of terrace shape is installed on the substrate 8 in order to match the height of the photo device 4 to that of the PLC part. Therefore, it is possible to transmit and receive digital signals of several gigabits.
However, in the conventional structure, which employs the three-dimensional optical coupling method using a vertical light receiving element, it is necessary to adjust the vertical position of the photo device—in the case of the single mode, and further position adjusting, assembling, and fixing operations must be performed within the error range of ±1 μm. Therefore, the prior art technique is problematic, in that more working errors may happen during the optical coupling process in comparison with the two-dimensional package having two degrees of freedom.